As a method for presenting information that users seek, a method of searching information in which users are requested to input keywords such as words or phrases, and documents, web pages, parts of sentences, photographs, voices, product information, and the like which are highly relevant to the keywords are presented is being broadly used in order to extract information that users seek from a large amount of media information such as documents or images. In addition, there are techniques such as similarity searching and associative searching in which information including not only keywords that users input but also synonyms thereof and words that are highly relevant to the keywords is also searched as a subject to be searched.
In addition, methods in which information that users will request is estimated and presented on the basis of the history of other users showing actions similar to the action history (purchase history of product, watched history of movie, and the like) of the users are being broadly used as recommend techniques, and particularly, a method such as collaborative filtering is being used.